This invention relates to a mixing device and more particularly to such a device which is especially adapted to efficiently transport and to mix developer compositions including toner, or other similar materials, such as are conventionally used in present day xerographic or electrostatic copying machines.
It turns out that current manufacturing methods for producing mixing or auger mechanisms or devices useful for mixing toners and like materials are extremely costly principally because machining and other expensive techniques are employed in the manufacture of such devices.
Accordingly, it is a primary object of the present invention to avoid the costly and difficult conventional methods of producing toner mixing devices and instead to provide an inexpensive molded or diecast mixer-auger for such purposes.
In accord with the primary object noted, it is a feature of the present invention that the mixing device is formed by stacking or longitudinally mating individual fin elements or sections constituting the essential parts of the device. Each of the fin sections may include a hub as part of the individual sections such that they are then suitably adapted to be attached to an extended shaft member. Alternatively, the shaft itself may be defined by, or constituted of, individual shaft sections each of which is integral with a particular fin section.
It will be appreciated that a variety of devices for the mixing and conveying of grains or like materials has been known in the art. In order to provide some background for the present invention reference may be made to the following U.S. Pat. Nos.:
319,311 D. Peters PA1 1,423,853 C. W. Hodgson PA1 1,558,580 A. J. Bishop PA1 1,795,792 P. W. G. Neilson
Whatever the merits of the devices disclosed in the afore-cited patents, their disclosures do not reveal mixing devices which can be readily adapted to the purposes here intended, that is, to the mixing and conveying of developer compositions, containing magnetic carrier particles and toner particles, and like materials. This is because in the operation of xerographic copiers it is critically important to have the toner particles mix readily and uniformly with the magnetic or iron carrier particles. Otherwise poor copies will result in the copying process stemming from this lack of uniformity in the mixture. A further reason is that the charging triboelectrically of the toner mix must occur with a minimum amount of damage to the iron carrier or else fatigue effects will be produced. Another important reason for having a specially constructed mixing device for mixing developer compositions is so that a low torque load will be imposed, thereby to minimize shearing effects and the like in the actual mixing operation.
A number of systems or devices which are specifically intended for the purpose of mixing developer compositions have been proposed in the prior art; among such are those disclosed in U.S. Pat. Nos. 3,639,051 and 3,333,566, which may be referred to for background material.
A further primary object of the present invention is to enable efficient, gentle mixing of developer compositions which contain magnetic toner.
Another primary object of the present invention is to enable flexibility in the mixing and conveying of the developer compositions.
In the attainment of the primary or fundamental objects, a variety of configurations is provided for the aforenoted fin elements or sections such that a combination of functions of mixing and transport of material may be selected by the operator. In particular, the mixing aspect is efficiently accomplished by a specific configuration involving bypass action, by which is meant that a portion of the material that is being conveyed is allowed to fall back or to be bypassed through openings provided in the helical fin areas. Accordingly, the bypass function can be achieved by having a plurality of like elements assembled in a longitudinal array or end-to-end relationship, these elements being either affixed on a shaft or integrally defining such shaft; if desired, one or more of the bypass-configuration fin elements can be utilized with other fin configurations as will be explained in detail hereinafter.
Other and further objects, advantages and features of the present invention will be understood by reference to the following specification in conjunction with the annexed drawing, wherein like parts have been given like numbers.